Annualr combustor

ABSTRACT

The disclosure illustrates an improved annular combustor having directional air inlets near the head end of the combustor tending to establish a vortex flow of combustion gases adjacent the combustor fuel nozzles. A series of jets downstream of the fuel nozzles reinforce the vortex flow of gases and deflects it into a horseshoe shape having legs generally parallel to the axis of the annular combustor. Cancelling jets downstream of the deflecting jets terminate the vortex flow and dilute it.

United States Patent Melconian Feb. 29, 1972 154] ANNULAR COMBUSTOR [72]lnventor: Jerry O. Melconian, Stratford, Conn.

[73] Assignee: Avco Corporation, Stratford, Conn.

[22] Filed: Nov. 25, 1970 21 Appl; No.: 92,808

[52] US. Cl ..60/39.36, 60/3965, 431/352 [51 Int. Cl. ..F02c 3/24 [58]Field oiSearch ..60/39.36, 39.65;43l/352 [56] References Cited UNITEDSTATES PATENTS Ellis ..60/39.65 Poyser Saintsbury ..60/39.65 Pierce..60/39.36

Primary Examiner-Douglas Hart Attorney-Charles M. Hogan 57] ABSTRACT Thedisclosure illustrates an improved annular combustor having directionalair inlets near the head end of the combustor tending to establish avortex flow of combustion gases adjacent the combustor fuel nozzles. Aseries of jets downstream of the fuel nozzles reinforce the vortex flowof gases and deflects it into a horseshoe shape having legs generallyparallel to the axis of the annular combustor. Cancelling jetsdownstream of the deflecting jets terminate the vortex flow and diluteit.

9 Claims, 4 Drawing Figures l l l I I I l 1 l 1 I l l I I l i I i r 'l nI 6 I I I ,1 i l I t I 'l I l l l INVENTOR. JERRY O. MELCONIANATTORNEYS.

ANNULAR COMBUSTOR The present invention relates to combustors for gasturbine engines and more specifically to annular combustors.

Fresentday annular combustors achieve a high level of efficiency andcompactness withmaximum energy release. One of the reasons for this isthat they incorporate air flow designs which establish vortex flowsadjacent the combustor fuel nozzles. Generally this promotesrecirculation of hot air adjacent the fuel nozzle to insure thatcombustion is maintained for widely varying flow rates and fuel/airratios.

With this type of arrangement the size of the annular combustor isgreatly decreased. However, since the combustion region is in anannulus, it requires a large number of fuel nozzles which accuratelymeter fuel flow to provide a uniform distribution of the hot gasesthroughout the circumference of the annulus. This'fact has limited theapplication of the annular combustor to small, economical gas turbineengines because the fuel nozzles for this purpose are extremelyexpensive. The large number required, even for a small combustor, makesan engine prohibitively expensive.

Accordingly, it is an object of the present invention to provide ahighly efficient annular combustor while at the same time substantiallyreducing the number of 'fuel nozzles required for its efficientoperation.

The above ends are achieved by a means formed in the walls of an annularcombustor to direct pressurized air in a vortex flow closely adjacent anozzle located in the upstream end of the combustor. A means downstreamof the vortex flow means reinforces the vortex flow and deflects it intotwo spaced downstream legs of vortex flow on either side of each of thenozzles. The axis of rotation of the vortex flow in the legs isgenerally parallel to the axis of the annular chamber.

The above and other related objects and features of the presentinvention will be apparent from a reading of the description of thedisclosure shown in the accompanying drawing and the novelty thereofpointed out in theappended claims.

In the drawing:

FIG. 1 is a fragmentary, longitudinal sectional view of a gas turbineengine which incorporatesan annular combustor embodying the presentinvention;

FIG. 2 is a view taken on'line 2-2 of FIG. 1 and-showing the annularcombustor of FIG. 1 in an unwrapped condition;

FIG. 3 is a view taken on line 3-3 of FIG. 1;

FIG.;4 is'an illustration of a combustor incorporating an alternateembodiment of thepresent invention.

Referring particularly to FIG. 1, there is shown an outer housing'l0 fora gas turbine engine, only a portion of which is shown, and a diffuserduct 12 cooperating with the outer housing to provide an annularperipheral flow path for pressurized air from a compressor (not shown).The airthat passes from the diffuser duct 12 enters a chamber 14 formedby the housing 10 and a coaxial turbine outlet duct 16.

Positioned in the pressure chamber 14 is an annular combustor generallyreferred to by reference character 18. Combustor 18 comprises inner andouter walls 20; 22, respectively, which are secured to an upstreamclosed end 24 having a series of circumferentially spaced fuel nozzles36(only one is shown). The inner and outer walls 20, 22 join outer andinner turbine inlet ducts 26,28 by a sliding thermal expansion jointtoform an open downstream outlet- 30. A turbine inlet nozzle assembly 32is secured to the downstream end of turbine inlet ducts 26 and 28. Abladed rotatable turbine wheel34 is positioned downstream of nozzle32.Turbine wheel34 may be one of a series of turbine wheels positionedalong dashed line 35 that are rotated by passage of hot gases from theturbine nozzle 32. However, only turbine wheel 34 is shown to simplifythe description of the invention.

In operation of the engine, pressurized air in chamber 14 enters theinterior of combustor l8'through openings to be described in detaillater and fuel is injected into the combustor 18 by fuel nozzles 36. Thefuel is mixed' with air and themixture ignited by suitable means toprovide a hot propulsive gas stream. The hot gas stream flows to thedownstream outlet 30 and is discharged from turbine inlet nozzleassembly 32 across bladed turbine wheel 34. The rotating output ofturbine wheel 34 is generally used to drive a bladed compressor whichsupplies pressurized air for the combustor 18. Downstream of turbinewheel 34 the hot gases may pass through successive power turbine stagesdriving. an output shaft or may be discharged through a nozzle toprovide a reaction propulsion for the engine.

In accordance with the present invention the combustor l8 incorporatesflow-directing features to be described below.

The upstream closed end 24 of the combustor 18 joins the outer'wall 22at a series of corrugations 38. The net effect of this is to form aplurality of inlet ducts 40 (see particularly FIG. 3) that admitpressurized air and direct it in an upstream direction, as shown by thearrows in FIG. 1, representing the flow of the air into the combustor.The upstream closed end 24 joins the inner wall 20 along a series ofcorrugations 42. This junction forms a series of inlet ducts 44 (seeFIG. 3) which direct air into combustor 18 in a downstream direction asshown in FIG. 1. Directly downstream of the nozzles 36 are a series offlow-deflecting inlet ducts 46 and 48.

As is apparent from FIGS. 1 and 2, these ducts are positioned so thatthe airflow'entering the interior of the combustor 18 through ducts 46and 48 has sufficient strength to reinforce and establish a strongvortex flow immediately adjacent the nozzles 36. This vortex flow in thevicinity of the nozzles 36 has an axis of rotation which extendscircumferentially relative to the annular combustor 18. Because the flowin the combustor 18 is toward the outlet 30, the vortex flowsestablished adjacent each nozzle 36 is deflected into two downstreamlegs L] and L These legs extend toward the outlet 30 and their axis ofrotation is generally parallel to the axis of the annular combustor 18.To cancel the vortex flow in legs L and- L a series of cancelling jetsare provided through openings 50, 52. These jets are positioned tooppose the direction of rotation of the vortex flow, as shownparticularly in FIGS. 2 and 3. Once the vortex flow in legs L and L hasbeen cancelled, suitable diluting .air is provided through openings 54to cool the mixture for discharge from outlet30.

Although it is not described herein, to enable a clearer understandingof the present invention suitable air inlets can be provided to filmcool the'inner' and-outer walls 20, 22, as is apparent to those skilledin the art.

During operation ofv the engine the air flow described above causes astrong vortex flow immediately adjacentthe nozzles 36. This flowrecirculates and maintains the hot downstream gases adjacent the nozzleto stabilize and maintain combustion. However,- the deflecting jets fromducts'46, 48 split the flow from: each nozzle to immediately distributethe combustion gases over a relatively .wide spacing. The result is twodiscrete legs which uniformly pass toward the outlet 30. It can be seenthat what has been accomplished with this arrangement is that thecombustion gases from each nozzle have been split and discharged over awide circumferential distance in the combustor 18. The net effect ofthis distributionis to provide the equivalent of a combustor utilizingtwice the number of nozzles astheconstruction shown above. Thisisillustrated inFIG. 2 where a series of center lines, designated N, areplaced in line with the axis of the legs of vortex flow. It can be seenthat-the resultant distribution of the combustor described above canonly be accomplishedin prior art designs by utilizing twice the'numberof nozzles. It isapparent that this construction,'while;retainingexcellent distribution, enables a substantial reduction in the cost ofan annular combustor, thereby permitting it to be used in relativelyeconomical arrangements.

FIG. 4 illustrates an alternate embodiment of the present invention asapplied to thick annular combustors for relatively large engines. Acombustor, generally indicated by reference character 60, comprisesinner and outer walls 62 and 64, respectively. An upstream closed end 66joins the inner and outer walls 62, 64 at a series of corrugations 68,70, respecnnimz an! a tively. The corrugations cooperate to form aseries of inlets which direct air in a downstream direction. A series ofholes 72, 74 for deflecting jets are positioned downstream of each oneof a series of fuel nozzles 76.

in operation, the flow of air past the corrugations 68, 70 tends to forma vortex flow. This vortex flow is greatly reinforced by the air jetsfrom the openings 72, 74. In addition, the air jets deflect theresultant vortex flow into circumferentially spaced axially directedlegs. The result of this is that the fuel flow from the nozzle 76 isdistributed into upper and lower vortex flows immediately adjacent itand the flow in the vortex flows is further split to distribute itcircumferentially around the annulus of the combustor 60.

For an equivalent annular combustor having a relatively thick annulus,the above arrangement enables a reduction in the number of nozzlesrequired to produce uniform distribution of the combustion gases. Inaddition, the efficient burning and mixing of the nozzles enables agreatly reduced length for the combustor which in turn enables asubstantial reduction in the length of the engine.

It is noted that this embodiment is particularly suited for straightthrough axial flow gas turbines since the corrugations 70 and 68 bothface in the direction of flow from an upstream located compressor. Thisarrangement, however, may be incorporated in a reverse flow engine suchas the one described in FIG. 1 by incorporating a turning duct adjacentthe corrugations 70 to turn the flow 180 for entry into the combustor,

While the combustor design of FIGS. 1-3 has been described in connectionwith an engine of the reverse flow type, it is apparent that thecombustor could be used in engines of the straight flow type by usingsuitable turning ducts without departing from the spirit and scope ofthe present invention.

Having described the invention, what is claimed as novel and desired tobe secured by Letters Patent of the United States is:

1. In a combustor comprising an annular walled chamber immersed inpressurized air and having an upstream closed end and a plurality ofcircumferentially spaced nozzles injecting fuel in an axial directionfrom the upstream end for combustion with pressurized air in saidchamber and a downstream lower pressure open end for dischargingcombustion gases therefrom, the improvement comprising:

means formed in the walls of said annular chamber for directingpressurized air in a vortex flow closely adjacent said nozzles andhaving the axis of rotation of the vortex flow extendingcircumferentially relative to said annular chamber; and

means downstream of said vortex flow means for reinforcing anddeflecting said vortex flow into two spaced downstream legs of vortexflow on either side of each of said nozzles and having the axes ofrotation of the vortex flows in said legs generally parallel to the axisof said annular chamber,

whereby the number of fuel nozzles for said combustor is substantiallyreduced.

2. Apparatus as in claim 1 wherein said vortex deflecting meanscomprises means defining at least one opening in the wall of saidannular chamber downstream of each nozzle for directing a jet of air ofsufficient strength toward the interior of said annular chamber toreinforce and deflect said circumferentially directed vortex flow intosaid downstream legs.

3. Apparatus as in claim 2 wherein said deflecting means comprises:

means defining a forwardly positioned opening and means defining aplurality of smaller downstream openings adjacent said forwardlypositioned opening.

4. Apparatus as in claim 1 wherein said vortex flow means comprises:

means for forming a series of openings around the circumference of onewall of said annular chamber for directing pressurized air into theinterior of said chamber in an up stream direction; means for forming aseries of openings on the opposite wall of said annular chamber fordirecting pressurized air into said annular chamber in a downstreamdirection whereby vortex flow is established.

5. Apparatus as in claim 1 further comprising means downstream of saiddeflecting means for defining air jets positioned to cancel out thevortex flow in said legs.

6. Apparatus as in claim 5 wherein said deflecting means comprises meansfor forming at least one opening positioned downstream of said nozzlefor directing a-flow of pressurized air in a jet toward the interior ofsaid annular chamber with sufficient strength to reinforce the vortexflow and deflect it into said two spaced downstream legs.

7. Apparatus as in claim 6 wherein:

said vortex flow means comprises means for forming a series of openingsaround the circumference of one wall of said annular chamber fordirecting pressurized air into the interior of said annular chamber inan upstream direction and means for forming a series of openings on theopposite wall of said annular chamber for directing air in a downstreamdirection whereby said vortex flow is established.

8. Apparatus as in claim 7 wherein said deflecting means comprises:

means defining a forwardly positioned opening and means defining aplurality of smaller downstream openings adjacent said forwardlypositioned opening.

9. Apparatus as in claim 1 wherein said chamber is relatively thick andwherein:

said vortex flow means is positioned on opposite walls of said chamberfor establishing two stacked vortex flows adjacent each of said nozzles;

said deflecting means is positioned on opposite walls of said chamberfor reinforcing each of said vortex flows and deflecting them into twospaced downstream legs of vortex flows, each having their axis ofrotation generally parallel to the axis of said annular combustor.

1. In a combustor comprising an annular walled chamber immersed inpressurized air and having an upstream closed end and a plurality ofcircumferentially spaced nozzles injecting fuel in an axial directionfrom the upstream end for combustion with pressurized air in saidchamber and a downstream lower pressure open end for dischargingcombustion gases therefrom, the improvement comprising: means formed inthe walls of said Annular chamber for directing pressurized air in avortex flow closely adjacent said nozzles and having the axis ofrotation of the vortex flow extending circumferentially relative to saidannular chamber; and means downstream of said vortex flow means forreinforcing and deflecting said vortex flow into two spaced downstreamlegs of vortex flow on either side of each of said nozzles and havingthe axes of rotation of the vortex flows in said legs generally parallelto the axis of said annular chamber, whereby the number of fuel nozzlesfor said combustor is substantially reduced.
 2. Apparatus as in claim 1wherein said vortex deflecting means comprises means defining at leastone opening in the wall of said annular chamber downstream of eachnozzle for directing a jet of air of sufficient strength toward theinterior of said annular chamber to reinforce and deflect saidcircumferentially directed vortex flow into said downstream legs. 3.Apparatus as in claim 2 wherein said deflecting means comprises: meansdefining a forwardly positioned opening and means defining a pluralityof smaller downstream openings adjacent said forwardly positionedopening.
 4. Apparatus as in claim 1 wherein said vortex flow meanscomprises: means for forming a series of openings around thecircumference of one wall of said annular chamber for directingpressurized air into the interior of said chamber in an upstreamdirection; means for forming a series of openings on the opposite wallof said annular chamber for directing pressurized air into said annularchamber in a downstream direction whereby vortex flow is established. 5.Apparatus as in claim 1 further comprising means downstream of saiddeflecting means for defining air jets positioned to cancel out thevortex flow in said legs.
 6. Apparatus as in claim 5 wherein saiddeflecting means comprises means for forming at least one openingpositioned downstream of said nozzle for directing a flow of pressurizedair in a jet toward the interior of said annular chamber with sufficientstrength to reinforce the vortex flow and deflect it into said twospaced downstream legs.
 7. Apparatus as in claim 6 wherein: said vortexflow means comprises means for forming a series of openings around thecircumference of one wall of said annular chamber for directingpressurized air into the interior of said annular chamber in an upstreamdirection and means for forming a series of openings on the oppositewall of said annular chamber for directing air in a downstream directionwhereby said vortex flow is established.
 8. Apparatus as in claim 7wherein said deflecting means comprises: means defining a forwardlypositioned opening and means defining a plurality of smaller downstreamopenings adjacent said forwardly positioned opening.
 9. Apparatus as inclaim 1 wherein said chamber is relatively thick and wherein: saidvortex flow means is positioned on opposite walls of said chamber forestablishing two stacked vortex flows adjacent each of said nozzles;said deflecting means is positioned on opposite walls of said chamberfor reinforcing each of said vortex flows and deflecting them into twospaced downstream legs of vortex flows, each having their axis ofrotation generally parallel to the axis of said annular combustor.